text: Electrofusion welds are performed by attaching a controlled power supply to the electrofusion fitting. There are typically two modes of operation.
  * Constant voltage
  * Constant current
  Constant voltage is typically used for high pressure pipelines such as mains gas and water. Fittings are fitted with a barcode specified to an ISO standard.
  Typically fittings will be welded at 39.5v, but manufacturers can choose voltages in whole numbers from 8 to 48v. The welding time is specified on the label in seconds or minutes